<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
	</body>
</html>
<script type="text/javascript">
	var a = 5;
	function aaa(){
		a=0;
//		this.a = 1;
		console.log(a)
		console.log(this.a) 	/* 打印函数的属性a */
		var a;
		console.log(a)
	}
	// 直接执行，this 指向 window
	aaa()	 /*0 5 0*/
	
	// new this指向自身
	new aaa() /* 0 underfind 0*/


	
	// *************************************************************************
	function bbb(){
		console.log(foo)	/* underfind*/
		var foo = 2;
		console.log(foo)	/* 2 */
		console.log(hello)	/* 报错，hello is not defined (没被定义)*/
	}
	bbb()
	

	

</script>